1. Technical Field
The present disclosure relates to zoom projection lens systems and, particularly, to a zoom projection lens system capable of maintaining optical performance during use.
2. Description of Related Art
Zoom projection lens systems are used in projectors to allow adjustment of effective focal length thereof and thus the projectors can be applied to different spaces, e.g., a spacious hall or a narrow room. When a projector is in use, it will produce large amounts of heat, and so glasses lenses are used in the zoom projection lens system instead of plastic lenses, because the coefficient of expansion of glass lenses is smaller than that of plastic lenses. But glass lenses are more expensive than plastic lenses, making the zoom projection lens systems more expensive to produce.
Therefore, it is desirable to provide a zoom projection lens system which can overcome the limitations described.